Concerning plural forms: crèmes brûlées follows the French plural, which requires that the adjective (brûlée(s) ‎(“burnt”)) agree in number with the noun it modifies (crème(s) ‎(“cream(s)”)); crème brûlées treats the phrase as a headless English noun, regularly suffixing -s to form its plural; whereas crèmes brûlée retains the nominal head, forming a plural by suffixation of the noun, per English grammar.